> When I was talking to someone the other day about the current TTL policy, he >was like "WTF, who would want that, it eats your data?" I don't think anyone is well served by that kind of shallow analysis.
The TTL feature was introduced for the convenience of having the system automatically garbage collect transient data. If you set a TTL on a column family, you are telling the system that the data shall expire after that interval elapses, that the data is only useful for the configured time period. If the data should not actually be considered transient, then configuring a TTL is the wrong thing to do -- at least currently. > "TTL except for most recent" HBASE-4071 is a useful and good idea. Best regards, - Andy Problems worthy of attack prove their worth by hitting back. - Piet Hein (via Tom White) >________________________________ >From: Ian Varley <ivar...@salesforce.com> >To: "user@hbase.apache.org" <user@hbase.apache.org> >Sent: Saturday, August 13, 2011 8:24 PM >Subject: Re: TTL for cell values > >So, what you're saying is: > >http://lmgtfy.com/?q=hbase+ttl+remove+all+versions+except+most+recent > >:) > >I like the idea of making this pluggable (via the coprocessor framework, or >otherwise). But I also think this is a fundamental enough policy option that >making it hard-coded might be a good idea. When I was talking to someone the >other day about the current TTL policy, he was like, "WTF, who would want >that, it eats your data?". There's no such thing as a "keep 0 versions" >option, and thus no way to accidentally lose your most current data using that >approach. But with the TTL version there is, which is (IMO) counter-intuitive >for those coming from an RDBMS background. > >Commented thusly in the JIRA. :) > >Ian > >On Aug 13, 2011, at 8:00 PM, lars hofhansl wrote: > >Hey Ian, (how are things :) > >I just stumbled across https://issues.apache.org/jira/browse/HBASE-4071. > >-- Lars > > >________________________________ >From: Ian Varley <ivar...@salesforce.com<mailto:ivar...@salesforce.com>> >To: "user@hbase.apache.org<mailto:user@hbase.apache.org>" ><user@hbase.apache.org<mailto:user@hbase.apache.org>> >Sent: Saturday, August 13, 2011 6:51 PM >Subject: TTL for cell values > >Hi all, > >Quick clarification on TTL for cells. The concept makes sense (instead of >"keep 3 versions" you say "keep versions more recent than time T"). But, if >there's only 1 value in the cell, and that value is older than the TTL, will >it also be deleted? > >If so, has there ever been discussion of a "TTL except for most recent" >option? (i.e. you want the current version to be permanently persistent, but >also want some time-based range of version history, so you can peek back and >get consistent snapshots within the last hour, 6 hours, 24 hours, etc). TTL >seems perfect for this, but not if it'll chomp the current version of cells >too! :) > >Thanks! >Ian > > > >
